Vibration is one of the most significant causes of failure but is not yet defined within the USP (it states ‘no significant vibration ’). Part of the problem is defining what limits should be acceptable as vibration varies with frequency. Vibration should be seen as excess energy which is transferred to the vessel and will increase the dissolution rate, 5-10% is easily possible. The most common cause of vibration is the water bath or a worn drive belt in the motor unit. Other causes of vibration are typically caused by other pieces of equipment on the same bench.